Light-emitting display elements such as organic EL elements display full-color images employing, for example, a so-called RGB method. In this RGB method, white light for white color display is synthesized after color lights emitted from light-emitting layers corresponding to R pixels, G pixels and B pixels are divided once through color filters. Thus, some of light emitted from the light-emitting layers is dampened by the color filters, which requires more electricity for maintaining the brightness of white light. In order to solve this problem, PTL 1 discloses a method in which full-color images are displayed using four pixels of R, G, B and W (white). In this method, unlike the above RGB method, white light is obtained with no use of a color filter; i.e., white light is directly emitted from light-emitting layers that emit white light. Therefore, white light can be emitted without being dampened by the color filter.
However, in the light-emitting display element emitting white light, external light enters the element through the optical path of white light, is reflected inside the element, and then is emitted again to the outside through the optical path of white light. As a result, display performances are adversely affected to cause problematic phenomena such as glare of outside views, and a decrease in contrast.
In order to solve this problem, PTL 2 discloses an organic EL element including a film substrate having an organic EL film laminated on one surface of the film substrate and a linearly polarizing plate provided on the other surface of the film substrate, wherein the film substrate serves also as a ¼ wavelength plate. This patent literature describes that, with this structure, the number of layers through which light passes to be emitted outside of the element becomes smaller than in conventional structures. Thus, light scattering at the interfaces between the layers is reduced to shield reflected light more reliably.
However, in the structure disclosed in the above patent literature, the linearly polarizing plate and the ¼ wavelength plate are provided not only in the optical path of white light but also in the optical paths of red, blue and green lights. In this structure, since the linearly polarizing plate is provided in the optical paths of red, blue and green lights, light transmittance is decreased to about 50% due to the presence of the linearly polarizing plate, problematically decreasing light use efficiency of the light-emitting element.